parser: Don't group patches with different versions in a series

parser: Don't group patches with different versions in a series

As noted in #340 [1], if a patch from a series is dropped or
miscategorised, patches from a later revision of that series can end up
included in the earlier series rather than in their own series. This was
actually intentional as part of the fix for #105 [2]. However,
completely ignoring this information can be problematic. Refine things
by checking for versions and, if they don't match, using timeboxing to
try guess if they should be kept together. This would resolve the issue
seen in #340 while preventing a regression for #105.

[1] https://github.com/getpatchwork/patchwork/issues/340
[1] https://github.com/getpatchwork/patchwork/issues/105

Signed-off-by: Stephen Finucane <stephen@that.guru>
Tested-by: Ali Alnubani <alialnu@mellanox.com>
Related: #340
Related: #105