various minor improvements, take 2

[yakra]

The first 5 commits are rebased from the last 5 in #505.

• 571e136closespython style floats: strcat -> strcpy yakra/DataProcessing#196. Refactors DB lines for Routes & ConnectedRoutes, and improves writing "Python-style floats", with a single .0 appended to integer values, to nearmisspoints.log & tm-master.nmp.
• 58b4b57 & 2e6dc1a are what they say on the tin.
• 26f5478 saves a tiny bit of RAM for each TravelerList.
• 5b68177 refactors finding the update date & time for each .list file upon construction of its TravelerList object.

The last 2 commits are redos of the first 2 in #505.
There are several ways to more effectively use C++'s std::unordered_map class. Changes that would have conflicted with the first 2 commits of #505 are redone here; other items can be explored in the future.

• 1672124 has the same diffs as d2cdcaa for 10 of 13 files, saving the other 3 for the next commit:
  • C++: mostly conceived as code-readability cleanup, but it ended up saving a little time on userlog generation, more noticeable on slower machines like lab3. Closesunordered_set::count yakra/DataProcessing#199.
  • Python: Minor cleanup that avoids having to create new list objects from objects that are already iterable/searchable.
• dd274f2 redoes HighwaySystem.cpp, Route.cpp & sql_file.cpp.
  Both before & after #505, time was wasted by searching hash tables twice -- once to determine membership and again to get the value for a given key.
  Before, we at least got the result of std::unordered_map::find, even if only to use it as a temporary & then just discard it.
  Here, that result gets saved & used a 2nd time, avoiding that 2nd lookup.
  Plus, we get rid of that unnecessary membership test as done in c8b3c98, described with the code snippets in #505's OP. Not its own separate commit this time around.

[jteresco]

all good to go to production?

[yakra]

Good to go.