custom excerpt

it now is possible to define what shall be in the excerpt.

when the string "---" is found or something is parsed as a <hr>, the
excerpt will go till that point.
filetype autoload

just a little autoload for the filetypes
image caching

create a new tool for the image caching. Whenever using images in a
file, this shall be called (\lorbeer\tools\image).
Merge pull request #7 from thephpjo/dev

excerpt, filetype, image caching