PHP8.0 support

fixed php8 notices, warnings and errors
refactored \arc\template::compile because create_function is now deprecated

Fixed issue in context::push

Context still used the old prototype api.

Fixed minor documentation issue

tree/NamedNode didn't extend from tree/Node, which was an empty abstract class anyway, but this generated errors in static code analysis. So fixed it here.

Updated to PHP 7.4 and PHPUnit 9

Also moved the prototype stuff to a seperate repository

Prototype Exceptions were incorrect

Merge pull request #27 from poef/master

fixed exceptions

PHP 7 compatibility

Also some changes that should have been in 2.0 but got left hanging.

now with PHP7 support and better exception names

We bumped the major version because this release is not fully backwards compatible.

• We decided to change some names to be less redundant.
• All exceptions have been renamed. If you check or throw arc exceptions, please see the new names.

Also we're now testing PHP 5.6 and PHP 7 only.
The remaining ARC libraries will be bumped to 2.0 as well, many have backwards incompatible changes as well.

arc-base: minor fixes, code cleanup and documentation updates

Fixed \arc\tree::sort callback handling
added the \arc\lambda documentation
fixed code style more to PSR-2