[FEATURE] Enable sheet compacting in individual Flux forms

WARNING: DO NOT USE DYNAMIC VARIABLES!
WARNING: IS DESTRUCTIVE WHEN CHANGED IN AN EXISTING ELEMENT!

Be very careful about this new toggle. Only use it in absolutely fresh content element templates - once data has been saved in either state, toggling the state destroys the database content; it can even potentially cause "invalid argument type for foreach" errors when using section objects in Flux forms.

In short: there are some pitfalls but using it on all new content templates is completely safe.
Merge pull request #49 from NamelessCoder/claus/compact

[FEATURE] Enable sheet compacting in individual Flux forms
[BUGFIX] Extend DataHandler override from TCEmain for compatibility

This change should allow the overrides to work on installs using hook processors which needlessly define a required class name on the fourth parameter of most TCEmain hook call dispatching functions.

Although this adds yet another class inheritance layer it's preferable to allowing unpatched third-party extensions such as TemplaVoila to fail.

Fixes: #22
Merge pull request #50 from NamelessCoder/issue/22

[BUGFIX] Extend DataHandler override from TCEmain for compatibility