`Copy()` and `MutableCopy()` methods for `Text` incorrectly handled
negative arguments in some cases. They were fixed and appropriate tests
were added.
Now all objects only have to calculate their hash code once and it's
value will be stored for later `GetHashCode()` calls, since has code is
not suppoed to change during their lifetime anyway.
This is a giga commit, something that should not really be done with
git, but I messed up.
This commit brings a great amount of changes, most important is
reworking `TextAPI` and alsmost complete replacement of `string` with
`Text`/`MutableText`.
Another huge change is introduction of command system that allows to
define commands in a centralized manner, handles auto-parsing of
their parameters and auto generates help info.
Lastly, JSON data types were replaced with new
`DynamicArray`/`AssociativeArray` that are better designed and more
generic.
Anton Tarasenko