Some minor refactorings

SPR-291

Save Schema-Data of pages for assigned Schemas

some refactoring in the form building

Now the whole form is inserted as a single HTML element. This makes it
easier to correctly position it in the form (the position is determined
dynamically now)

some refactoring in the form building

Now the whole form is inserted as a single HTML element. This makes it
easier to correctly position it in the form (the position is determined
dynamically now) than to have to work with permanently shifting
positions witin the form object. Since we don't expect other plugins to
modify our form this shuld be okay.

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minor name cleanup

also always use protected instead of private as we may need to access
internals during testing later on

use $REV to load old schema data when editing old revision

columns are already sorted. no need to sort again

objects are always passed by reference

Show simple Schema-Form to enter values

SPR-291

made autoloader function static

this makes it easier to reuse in testing

some more PHP docs for better understanding

a first go at the overall structure. far from complete

initial wizard generated structure