Version argument in Resource object is ignored when initializing a WikiPage

[Ryan J Ollos]

The version of the Resource object is ignored when initializing a WikiPage object.

Python 2.7.4 (default, Sep 26 2013, 03:20:26) 
[GCC 4.7.3] on linux2
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>>> from trac.env import Environment
>>> from trac.resource import Resource
>>> from trac.wiki.model import WikiPage
>>> env = Environment('/home/user/Workspace/t11518/tracdev')
>>> resource = Resource('wiki', 'WikiStart', 1)
>>> page = WikiPage(env, resource)
>>> page.version
4

This was previously discussed in comment:4:ticket:11518. It was suggested to also allow the version parameter to take precedence over Resource.version, which would preserve existing behavior.

We should also:

• Improve the behavior when version can't be cast to an int, as exhibited by the tests: trunk/trac/wiki/tests/model.py@12587:285-295#L285​. Should an invalid version by coerced to None?
• Improve docstring for WikiPage.