Add dumpstrobes --seeds option for writing out the full seed vector

[marcelm]

With this, dumpstrobes --seeds genome.fa dumps the sorted randstrobes vector to standard output in a comma-separated format.

Columns:

• hash
• position
• reference index
• strobe 2 offset

I also had to move two functions in index.cpp into an anonymous namespace as otherwise the linker complains about a duplicate name (count_randstrobes exists twice).

[ksahlin]

Thanks! Approved.