Add server side element methods to Dynamic

An example of finding the first button's name attr.

mobile :find, [ [ [26, '(?i).*button.*'], [100] ] ]
post
session/d1fe1c05-3ec3-49a9-80bd-394ebf726ba6/execute
{"script":"mobile: find","args":[[[[26,"(?i).*button.*"],[100]]]]}
=> "Sign In"
Add all to mobile: find

For example, return the name value of all edittexts.

> mobile :find, [ 'all', [ [26, '(?i).*edittext.*'], [100] ] ]
post
session/5dc30124-994f-48e6-83a8-fb1d18a7d361/execute
{"script":"mobile: find","args":[["all",[[26,"(?i).*edittext.*"],[100]]]]}
=> "[Email Address, Password]"
Merge pull request #449 from bootstraponline/dynamic_attr

Dynamic attr