[BUGFIX] Use provided variables' checksum as name part

Before: only when `fluid="TRUE"` would the variables be considered.

After: if `arguments` is filled with any value, variables are considered and will add a uniqueness checksum to the Asset filename.

Fixes: #210
[DOC] Change description of argument `arguments` on Assets
Merge pull request #235 from NamelessCoder/assetvariableschecksum

[BUGFIX] Use provided variables' checksum as name part
[BUGFIX] Checksum gets lost when processing dependencies

Asset names containing the checksum are saved as array keys which get lost during the processing of dependencies.
Merge pull request #238 from bjo3rnf/assetchecksum

[BUGFIX] Checksum gets lost when processing dependencies