Handle non-Tor versions correctly in metrics graphs

sysrqb notes that https://metrics.torproject.org/network.html#versions only shows Tor versions and omits, for example, node-Tor relays. In fact, servers.csv does list node-Tor relays, but in a broken way:

2014-01-23,,,-Tor,,,3,
2014-01-23,,,0.2.2,,,306,
2014-01-23,,,0.2.3,,,2289,
2014-01-23,,,0.2.4,,,2382,
2014-01-23,,,0.2.5,,,100,

Two things need fixing here:

• servers.csv should contain the number of "Other" versions if a version string does not begin with "Tor "; rather than simply cut off the first 4 characters.

• The graph should contain a line for "Other" versions; rather than simply omit them.