Tooltips

[narc0tiq]

We have some slightly obscure things happening sometimes, and it would be good to have the ability to use tooltips to clarify when possible.

For instance:

• "Insufficient data..." can tooltip-explain that this indicates not enough samples have been acquired to be able to calculate a rate of change; if the condition persists past the first minute or two of game time, you should consider changing your settings such that either there are more samples kept, or there is a longer interval between samples.
• "ETD: x" and "ETF: x" can explain that the initialisms refer to "Estimated Time to Depletion" and "Estimate Time to Full". ETF can further show what amount represents "full" (i.e., the largest known value for that signal, see also Colorization and percent of...? #12).
• "xx%" (not yet extant, but see Colorization and percent of...? #12) can show the number of which the current value is a percentage of (i.e., the largest known value for that signal).

All the buttons obviously also need tooltips -- they're pure graphics. They do occupy less space, but are thereby obscure enough to need explaining for new players.