Allow limiting of number of results returned by remote API

This will be useful for the following API methods:

• changesets
• query

As they can return large numbers of results, depending on their arguments.

changesets

This will be implemented by allowing the optional specification of a maxReturn parameter. This will overrides the already present maxReturn (previously hardcoded to 3000) and will be returned as part of the changesets object. To limit the impact on FishEye 3000 will be continue to be the highest specifiable max value.

query

This will be implemented as an additional EyeQL clause, identical in syntax and function to SQL's LIMIT clause. This will facilitate paging and/or raw limiting of the number of results returned.