This allows calling 'git cl try' with properties. Each
property is set with the option -p key=value, where value
will be treated as json if possible or as string.

Examples for -p and pitfalls:

key=string -> 'string'
key=1 -> 1
key=[1,2,3] -> [1,2,3]
key=["one","two","three"] -> '[one,two,three]'
'key=["one","two","three"]' -> ['one','two','three']

BUG=488235

Review URL: https://codereview.chromium.org/1339073002

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@296683 0039d316-1c4b-4281-b951-d872f2087c98