Bug: Fixed neat folding to refer to functions using qualified name.

Testing: Neat folding works for viewing variables.
Removed unwanted characters from indentation while viewing variables.
Test classes to be used for manually testing debug functionality.
Bug fix to exclude projects that don't exist while adding to debug
context.
Code refactor.

* Created context classes for variables and stackframes and changed
  commands to use them.
* Track all active threads in ThreadContext.
Status command to view current threads and variables.

:JavaDebugStatus command will open a temp window in the bottom and
vertically split it. One one side it will show the threads and another
side it will show the variables of the currently suspended thread.

This is just an initial checkin. Needs more display formatting.

Testing:
Verified the command shows threads and variables.
Enhancements to debug status view.

* Display status when :JavaDebugStart command is run. It does not auto
  refresh yet.
* util.vim: Enable creation of temp window with vertical split. There
  are some issues in this code, so its not used by debug.vim in this
  change. So the thread view and variable view are shown as horizontal
  splits. This will be fixed in next CL.

Testing:
Status window shows correctly after starting a debug session.
Test code.

* Simulate multiple threads to test stackframes.
Auto update debug status view.

* When debug events get fired, the status window is updated using
  VimClient.refreshDebugStatus which in turn triggers a VIM command to
  request for the debug status. So the control flow is:
  Java->VIM->Java->VIM.
* DebuggerContextManager: New class to keep track of debugging sessions.
  With this change, DebuggerContext is created and destroyed for each
  session instead of getting reinitialized. It makes the code cleaner
  and gets rid off race conditions due to re-initialization.
* debug.vim: Moved the :JavaDebugStatus outside of ftplugin into plugin
  dir. This is necessary because this command is invoked from an
  external VIM command. If at this time, the cursor is not in a Java
  file, then the command won't be available if it were defined in a
  ftplugin dir.

Testing:
Verified the debug commands, status command.
coding style updates for new java debug code
fix message key in DebugStartCommand
rename java debug breakpoint toggle command

- rename the command to toggle breakpoints to make it easier for users
  to scan wildmenu completion for the command.
- rename the java class as well, grouping breakpoint commands together
  (again, easier to scan the list and locate the file)
fix java debug vertical temp windows

not perfect since there are resizing issues as other windows are opened
and closed, but this makes it functional as a start.