English language fix
GitPropertyValidator: improve error message when commit is rejected due to wrong properties

Fixes #46
Merge pull request #47 from slonopotamus/reject_properties

GitPropertyValidator: improve error message when commit is rejected due ...
Pluggable properties mapping.
Reformat code.
Merge branch 'pluggable-properties'
Split SVNContext.getFile for urls and paths

URL access requires permission check. Fixes #49.
Merge pull request #51 from slonopotamus/url_vs_path

Split SVNContext.getFile for urls and paths
Improve error handling

  * Prefer SVNErrorCode constants over hardcoded numbers
  * Throw SVNException instead of BaseCmd.sendError + return
  * Use more specific error codes where appropriate
Merge branch 'error_codes'

* error_codes:
  Improve error handling
Merge branch 'master' into persistent-cache