Deprecate participle as part of speech

The morph retriever returns verb now for all participles. We remove it
as a distinct part of speech category in our morph conf files.

Breaks backwards compatibility. We will have to fix the old treebank
data with this. The introduction of the new schema might be a good
opportunity to do this.
Add unless dependency handling in mFC
Allow an asterisk in mFC dependency handling
Change dependency logic in mFC and introduce rules

Allows much more fine grained attribute sets. Changes to the attribute
files will soon be commited, check out the new syntax there.
Allow arrays and strings in morph attribute rules
New rules syntax in gr_attributes.json

This is a non-working commit, but done on purpose, as only a single
attribute (Number) is changed. It shall be used for referencing the new
syntax.

Attributes take an array of rule object. Such a rule can have two
properties: "if" and "unless". Both properties have to be objects again.

These objects take other attribute names as keys and a string value or
an array of string values.
Add morph.rulesOf(), deprecate dependenciesOf()
Change gr_attributes conf file to new rule syntax
Merge pull request #228 from latin-language-toolkit/deprecate_the_participle

Deprecate the participle and adds new rule syntax in morph (gr only!)