Add test for issue 2811: (1/(1-t)).subs(t,1) returns zoo after a078ac2
give Dummy a sort key
minor edits
unXFAIL ask(Q.real(NaN)) is None tests

Note: the old assumptions return None for queries about NaN whereas
the new assumptions (because NaN gets handled by _number) returns
False -- if it is important that this return None, the following can
be added to the pertinent handlers:

    NaN = staticmethod(lambda x, y: None)
sort assumptions dict when printing
more granular separation of re and im parts of Pow
modify old assumptions for Pow
Merge pull request #3002 from smichr/dsort

give Dummy a sort key
modification of new assumptions
do not conclude if there is no precision
modify AskPositiveHandler.log

Also changed ~negative to nonnegative since ~negative does
not imply that the number is even real: it could be imaginary
or positive or zero. nonnegative implies that the number is
real and is not 0 or negative (and that's what the test in Add
is looking for).
code quality: check for duplicate test_ functions
Merge pull request #2967 from skirpichev/2811-test

Add test for issue 2811: (1/(1-t)).subs(t,1) returns zoo after a078ac2
rework handling of re/im in solve
raise error if Abs-arg is not real or imag
Merge pull request #2927 from smichr/abs

issue 4046: better handling of Abs by solve
fix AskPositiveHandler.Pow

There was a duplicate .even test; the second one should have
been odd. It was not caught the last time changes were made
to these lines, probably because the change was automated. I
found the need for a change because this was a line that was
uncovered with tests.

Other tests were also added to bring the coverage in `sets` almost
to 100% (the handling in _number is not complete but may represent
lines that will be unreachable/unlikely). In the `order` file there
is a significant amount of code for the hermitian property that
is not covered.
add inline note about use of (-1)**i
Merge pull request #2952 from smichr/reim

assumptions modifications for imaginary bases
travis: Run apt-get update for TEST_SPHINX