Fix crash at startup on Windows

[HebaruSan]

Problem

If you run the master HEAD version in Windows, you get this exception at startup:

Unhandled exception:
System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
 ---> System.ArgumentNullException: Value cannot be null.
Parameter name: container
   at System.Windows.Forms.ContextMenuStrip..ctor(IContainer container)
   at CKAN.SettingsDialog.InitializeComponent()
   at CKAN.SettingsDialog..ctor()
   --- End of inner exception stack trace ---
   at System.RuntimeTypeHandle.CreateInstance(RuntimeType type, Boolean publicOnly, Boolean noCheck, Boolean& canBeCached, RuntimeMethodHandleInternal& ctor, Boolean& bNeedSecurityCheck)
   at System.RuntimeType.CreateInstanceSlow(Boolean publicOnly, Boolean skipCheckThis, Boolean fillCache, StackCrawlMark& stackMark)
   at System.Activator.CreateInstance[T]()
   at CKAN.ControlFactory.CreateControl[T]()
   at CKAN.Main.RecreateDialogs()
   at CKAN.Main..ctor(String[] cmdlineArgs, KSPManager mgr, GUIUser user, Boolean showConsole)
   at CKAN.GUI.Main_(String[] args, KSPManager manager, Boolean showConsole)
   at CKAN.CmdLine.MainClass.Gui(KSPManager manager, GuiOptions options, String[] args)
   at CKAN.CmdLine.MainClass.RunSimpleAction(Options cmdline, CommonOptions options, String[] args, IUser user, KSPManager manager)
   at CKAN.CmdLine.MainClass.Execute(KSPManager manager, CommonOptions opts, String[] args)
   at CKAN.CmdLine.MainClass.Main(String[] args) 

Cause

This line initializes the purge button dropdown menu from #2536 in the settings window:

CKAN/GUI/SettingsDialog.Designer.cs

Line 44 in 681dd7e

this.ClearCacheMenu = new System.Windows.Forms.ContextMenuStrip(this.components);

However, this.components isn't currently being set. In the main form from which the above line was borrowed, there's a line to set it, but this isn't present in the settings form:

CKAN/GUI/Main.Designer.cs

Line 31 in 681dd7e

this.components = new System.ComponentModel.Container();

We should have copied and pasted this when we made the dropdown, but it's not apparent that it's required or might be missing.

Changes

Now this.components is initialized in the settings window and the exception is gone.

The cache settings text boxes are also made 5 pixels taller, since they were a bit squished on Windows previously.