Optimize identifier completion and do not crash anymore when clicking many...

Optimize identifier completion and do not crash anymore when clicking many times on the project remove icon in recent project list.

[DEVELOPMENT ENVIRONMENT]
* NEW: Rename source code directory 'Subversion' as 'VersionControl'.
* OPT: Completion of identifiers is faster.
* NEW: New icon emblem for symbolic links.
* BUG: Do not crash anymore when clicking many times on the project remove icon in recent project list.