[TASK] Be a bit less eager to remove Asset files

This should help improve VHS's performance greatly on sites which use a lot of Assets; before this change, VHS would remove Asset files on any type of cache clearing and would not hesitate to remove Asset files multiple times in one Request. After this change removal of files is only ever allowed once per Request and is only done when clearing _all_ caches in the backend, ensuring it doesn't happen too often (e.g. whenever an editor saves a page or clears the page content cache).
[BUGFIX] Override default value for argument 'as' in deferred menu ViewHelper

Due to the new default value for argument 'as' in menu ViewHelpers automatic rendering was disabled in deferred menu ViewHelper.
Merge pull request #251 from bjo3rnf/asfix

[BUGFIX] Override default value for argument 'as' in deferred menu VH
Merge pull request #250 from NamelessCoder/cache

[TASK] Be a bit less eager to remove Asset files
[DOC] Notice about faulty PHP Version 5.3.3 in README
Merge pull request #253 from cedricziel/php533errorNotice

[DOC] Notice about faulty PHP Version 5.3.3 in README
[BUGFIX] Fix exposure to "duplicate variables" issue in sub menu VH
Merge pull request #255 from NamelessCoder/subvh

[BUGFIX] Fix exposure to "duplicate variables" issue in sub menu VH
[BUGFIX] Do not reset "is parent" state after sub menu renders
Merge pull request #256 from NamelessCoder/subvh

[BUGFIX] Do not reset "is parent" state after sub menu renders
[TASK] Enable inline usage
[TASK] Add early return to avoid PHP warnings for NULL values
[TASK] Inherit relocated class
[TASK] Incorrect exception message
[TASK] Reorder conditions according to CGL
[BUGFIX] Check if linked asset exists before copying to avoid PHP warnings
Merge pull request #257 from bjo3rnf/inline

[TASK] Enable inline usage
[TASK] Add syslog warning about missing asset files
[TASK] Avoid PHP warning in case of empty array
[BUGFIX] Restore default name "rootLine" in breadcrumb "as" argument