Add function to initialize a project

- Add code to create the project folder, properties file and call the
  refresh project action. It ask the user for the needed info.
Change ProjectInit to be portable

- Extracted the related functions to a new file apexProject.vim
- Changed the code to reuse some of the plugin functions and to use
  portable functions instead of shell commands
- Changed the code that generates the package.xml to use spaces instead
  of tabstop, it prevents the override warning when refreshing
- Add documentation to the force.com.txt file
Remove doblequotes from apexOs#exe
Fix some typo in the help
Fix project name with spaces bug in apexProject#init

I was escaping the name with fnameescape() before calling
apexOs#createDir that escape the name again.
Add global commands file

- Created a new folder under vim-foce.com named global. This is inteded
  to contain all the *.vim files that need to be global and not
  restrained to Force.com file types.
- Added a new file global/globalCommands.vim to add the ApexInitProject
  command and it's related function.
- Added the new globalCommands.vim include to the .vimrc settings of the
  README.md file
- Also cleaned the code and added error management to prevent an error
  in the apexProject#init function when the current buffer has unsaved
  changes. In that case it will open the project folder in a new tab.
Merge branch 'master' of https://github.com/adegregorio/vim-force.com into adegregorio-master
proper initialisation and initial load fixes

- to load with vim :ApexInitProject must be in 'plugin' subfolder
- when creating local project against existing org - open existing class as the last step of the process to show that this org is not blank
- for blank orgs  (i.e. no classes) offer to create new file as the last setp in project creation wizard