Add simple vim mode

This commit adds a "vim_mode" setting (false/`0` by default) that causes
keys to be remapped in the following way by the `ScreenManager`:

+ h -> LEFT
+ j -> DOWN
+ k -> UP
+ l -> RIGHT
+ LEFT -> h (toggle help)
+ DOWN -> j (noop)
+ UP -> k (open kill menu)
+ RIGHT -> l (lsof current process)
+ K (Shift+K) -> k (open kill menu)
+ J (Shift+J) -> K (toggle show/hide kernel threads)
+ L (Shift+L) -> l (lsof current process)

I couldn't figure out where the manpage documentation is in the repo,
though I admittedly did not look particularly hard.

I believe this change would be a welcome option for heavy vim users like myself
who would like a familiar way to get around in htop.

Settings.c

@@ -31,7 +31,7 @@ typedef struct {
 
 typedef struct Settings_ {
    char* filename;
-   
+
    MeterColumnSettings columns[2];
 
    ProcessField* fields;
@@ -58,6 +58,7 @@ typedef struct Settings_ {
    bool updateProcessNames;
    bool accountGuestInCPUMeter;
    bool headerMargin;
+   bool vimMode;
 
    bool changed;
 } Settings;
@@ -114,7 +115,7 @@ static void Settings_defaultMeters(Settings* this) {
       this->columns[i].modes = xCalloc(sizes[i], sizeof(int));
       this->columns[i].len = sizes[i];
    }
-   
+
    int r = 0;
    if (this->cpuCount > 8) {
       this->columns[0].names[0] = xStrdup("LeftCPUs2");
@@ -134,7 +135,7 @@ static void Settings_defaultMeters(Settings* this) {
    this->columns[0].modes[1] = BAR_METERMODE;
    this->columns[0].names[2] = xStrdup("Swap");
    this->columns[0].modes[2] = BAR_METERMODE;
-   
+
    this->columns[1].names[r] = xStrdup("Tasks");
    this->columns[1].modes[r++] = TEXT_METERMODE;
    this->columns[1].names[r] = xStrdup("LoadAverage");
@@ -165,13 +166,13 @@ static void readFields(ProcessField* fields, int* flags, const char* line) {
 
 static bool Settings_read(Settings* this, const char* fileName) {
    FILE* fd;
-   
+
    CRT_dropPrivileges();
    fd = fopen(fileName, "r");
    CRT_restorePrivileges();
    if (!fd)
       return false;
-   
+
    bool didReadMeters = false;
    bool didReadFields = false;
    for (;;) {
@@ -244,6 +245,8 @@ static bool Settings_read(Settings* this, const char* fileName) {
       } else if (String_eq(option[0], "right_meter_modes")) {
          Settings_readMeterModes(this, option[1], 1);
          didReadMeters = true;
+      } else if (String_eq(option[0], "vim_mode")) {
+         this->vimMode = atoi(option[1]);
       }
       String_freeArray(option);
    }
@@ -320,12 +323,13 @@ bool Settings_write(Settings* this) {
    fprintf(fd, "left_meter_modes="); writeMeterModes(this, fd, 0);
    fprintf(fd, "right_meters="); writeMeters(this, fd, 1);
    fprintf(fd, "right_meter_modes="); writeMeterModes(this, fd, 1);
+   fprintf(fd, "vim_mode=%d\n", (int) this->vimMode);
    fclose(fd);
    return true;
 }
 
 Settings* Settings_new(int cpuCount) {
-  
+
    Settings* this = xCalloc(1, sizeof(Settings));
 
    this->sortKey = PERCENT_CPU;
@@ -344,7 +348,7 @@ Settings* Settings_new(int cpuCount) {
    this->cpuCount = cpuCount;
    this->showProgramPath = true;
    this->highlightThreads = true;
-   
+
    this->fields = xCalloc(Platform_numberOfFields+1, sizeof(ProcessField));
    // TODO: turn 'fields' into a Vector,
    // (and ProcessFields into proper objects).
@@ -375,7 +379,7 @@ Settings* Settings_new(int cpuCount) {
          htopDir = String_cat(home, "/.config/htop");
       }
       legacyDotfile = String_cat(home, "/.htoprc");
-      
+
       CRT_dropPrivileges();
       (void) mkdir(configDir, 0700);
       (void) mkdir(htopDir, 0700);