Consider consolidating several like files in the page load process

(from [9c51af40cdffb857ff0a9f49cd295545f4fa66ef]) Changed references to exponent_common.php to exponent_bootstrap.php since exponent_common was simple and also redundant of what was already in exponent_bootstrap.php. [#234 Consider consolidating several like files in the page load process] https://github.com/exponentcms/exponent-cms/commit/9c51af40cdffb857...

(from [dbfcc88ba9163ed736416b22bde0798d9a67ce64]) Loading of exponent_constants.php was moved earlier into exponent_bootstrap.php for standardization. Loading of subsystems/themes.php was stripped out of exponent_constants.php and put into exponent.php where is was being loaded earlier. [#234 Consider consolidating several like files in the page load process] https://github.com/exponentcms/exponent-cms/commit/dbfcc88ba9163ed7...

(from [c73b253790b4a49b8d240a483c821b0e88282fff]) A seemingly major change because of the filenames, but a Minor revision to the exponent "bootstrap" process to streamline it and give it a more linear flow. exponent_variables.php renamed to exponent_constants.php which was in turn renamed to exponent_constants2.php before it'll be deleted. Contents were moved into other file with config dependant constants being moved inot exponent_bootstrap.php
exponent_setup.php was renamed to exponent_php_setup.php since that's it's function and the environment constants were moved into exponent_constants.php.
[#234 Consider consolidating several like files in the page load process] https://github.com/exponentcms/exponent-cms/commit/c73b253790b4a49b...