Implemented composite pattern for filesystem

[schlingling]

closes #131

extends #123 and #219

Introduces a clean composite pattern for all filesystem related artefacts like it is done in ADAP.

The naming convention of the .ts-files yields the class-hierachy, so it is easier to understand.

[schlingling]

@rhazn FYI, since you are on leave, i requested Felix for an Review :)

[rhazn]

Thank you, if this is still open next week ping me and I can take a look then as well. If Felix is fine with it that's enough as well of course.

[felix-oq]

To avoid the instanceof checks, consider introducing new methods in FileSystemNode that perform the recursive descents. Those can then be called in the FileSystem class.

Also I think that paths should generally be treated case-sensitive.

[schlingling]

To avoid the instanceof checks, consider introducing new methods in FileSystemNode that perform the recursive descents. Those can then be called in the FileSystem class.

Also I think that paths should generally be treated case-sensitive.

all implemented with new commits including Design for uniformity.

[felix-oq]

A few more hints for improving the implementation, but otherwise this is good to go.