Renamed AttackTesla into AttackCharge and improved it.

Delay for initial charge is no longer hard-coded and can be customized now.
Same for delay between each charge.
Changed default MaxCharges to 1.
Added descriptions (except for MaxCharges since it's self-explanatory).
Adapts Tesla Coil and Obelisk to AttackTesla -> AttackCharge changes.

Fine-tunes Obelisk charge delay, adds changelog entry.
Un-hardcodes charge sequence name.
Fixes unused fields.
Adds UpgradeRule for AttackTesla -> AttackCharge.
Merge pull request #4803 from reaperrr/obelisk-fix2

Building charge improvements