[ABW]: [Fix] custom ops are no longer processed separately from other - helps when such ops target results of regular ops, posts in particular (see issue 162)
Added mock tests to show such problems for community post muting (fixed by above changes) and reblogs (not fixed)

added mock tests to show behaviour when community custom op targets deleted post or post from different community
[Note] because custom ops are processed separately from comments we have no guarantee that the processing will be valid (see comments in MR)

Changed behavior of notify::setLastRead custom operation - right now passed date exceeding head block time is implicitly corrected to head block time.
Also there was relaxed syntax: `date' field is optional (can have also null value) what also leads to saving head block time as lastRead time specific to the account related to operation.
Prepared initial set of trivial mock tests (to be continued).

for the first time used mock mechanism to introduce artificial vops
[Fix] eliminated expectation for mock vops to have timestamp

WIP: [ABW] added couple more non-pinned posts to the community to be able to test mixed paging; restored partial fix for paging problem

[ABW]: [Fix] mocks, particularily community related containing new posts, moved back in time by 2000 blocks so they don't push out regular posts from results
Needed to restore some tests that degraded over time, mostly with creation time sort of posts mixed with muting functionality
[Fix] Mocks no longer have anything other than transactions (if they do, it will be ignored anyway) - prevents incorrect values, especially previous and block_id
[Fix] Disabled printing whole mocks to log - it was just spam
[Fix] Empty mock can no longer contain erroneous link to previous block
[Fix] Fixed incorrect permlinks in some mock post mutes
[Fix] Fixed check for start post in pinned post query for bridge.get_ranked_posts with created/trending sort
[Fix] Added validation of community parameter for various bridge_api community related calls; also fixed order of checks and error messages
[Fix] Fixed paging and order in bridge.list_communities
[Fix] Custom SQL exceptions now have explicit custom codes CEHM1..8 - such code is now used (instead of message string) to determine specific exception
Extended checks or added logging for various erroneous situations during sync as well as mock related