svn: Refactored SvnConfiguration - code simplified, fields renamed
svn: Implemented ability to configure ssh tunnel for svn command line client in Subversion Settings
IDEA-130923 Run ContentRevisionCache.clearScope() logic under read action

Previous ContentRevisionCache.clearScope() logic performed custom lock and then implicitly run read actions during calls to VcsDirtyScope.belongsTo() - so deadlock could occur when ContentRevisionCache.clearScope() (or other method that also requires corresponding custom lock) is called simultaneously from other thread under write action.
To prevent such cases all ContentRevisionCache.clearScope() logic is wrapped with read action.
svn: Refactored ForNestedRootChecker - code simplified, @NotNull, inlined "goIntoNested" parameter of getAllNestedWorkingCopies() (as its value is false for all code paths)
IDEA-130628 Only check directories (and not both files and directories) while detecting svn working copies for project
IDEA-130628 Optimized svn working copies detection logic - only run "svn info" command on directory if it is either root directory (the one where detection was started) or has ".svn" child directory
Merge branch 'svn_18_3'