Code Cleanup: Json lexer memory leak

.. possibly. According to the docs we need to free
the malloc'ed memory in the lexer when parsing completes.
Code Cleanup: RideFile EditorData memory leak

.. when freeing memory for the ridefile we didn't delete
the memory allocated for editor data
Code Cleanup: Deprecate Train Streaming

We no longer support streaming data from the Train View.
All the source for this has been moved to deprecated.
Code Cleanup: RideFileCache remove mallocs

Mark Rage's superfast meanmax computer works like a charm but
uses stdlib malloc/free for memory allocation.
Update INSTALL-LINUX for needing > Flex 2.5.9
Support old flex or lex

.. in JsonRideFile.l

Because we added a call to yy_lex_destroy in the parser
but it may not exist in Flex < 2.5.9 or if we are not using
GNU Flex, e.g. good ol' ATT lex.
UI Nits: Diary Sidebar

.. alignment and spacing.
UI Nits: Less vibrant gradients

.. go back to more GC-like color defaults, which became a little
too vibrant in a recent update to introduce linear gradients to
the CP, Histogram and LTM plots.
Add Strava activity download feature