E3-653: Cleanup docs folder

See merge request e3/e3-require!65

E3-665: Allow other header files to be installed

See merge request e3/e3-require!64

e3-642: Use different variable names each time memory is allocated

See merge request e3/e3-require!63

E3-422: No more siteApps

See merge request e3/e3-require!61

Improved tests to actually check error messages

See merge request e3/e3-require!62

Improve debug log for module building

See merge request e3/e3-require!60

E3-186: Removed 'dev' targets for local source mode.

See merge request e3/e3-require!59

Local source mode can theoreticaly run 'make devbuild' and other related targets. However,
this yields somewhat undefined behaviour, since those will potentially be missing configuration
data or clashing with the regular build location. There is no reason to include dev targets for
local source mode, so they should be removed.

E3-186: Combine configure/E3 and configure/modules

See merge request e3/e3-require!56

Synchronised all of the config files in configure/E3 and configure/modules in order to merge the two configuration directories.

E3-518: Cleaned up _DB/_TEMPLATES

See merge request e3/e3-require!58

E3-546: Address flaw in make init process

See merge request e3/e3-require!57

E3-517: Cleanup `make vars`

See merge request e3/e3-require!55