Remove chain head distance dependent <v9 conditional code

[denravonska]

We are long into v9 blocks now and can start removing checks which depend on both <v9 blocks and being close to the chain head. For example:

Gridcoin-Research/src/main.cpp

Line 2354 in 5d8e4d7

bool fNeedsChecked = BlockNeedsChecked(block.nTime) || block.nVersion>=9;

Gridcoin-Research/src/main.cpp

Line 3570 in 5d8e4d7

if ( (pindex->nHeight % 60 == 0) && IsResearchAgeEnabled(pindex->nHeight) && BlockNeedsChecked(pindex->nTime))

Gridcoin-Research/src/main.cpp

Line 4187 in 5d8e4d7

if (IsResearcher(bb.cpid) && IsProofOfStake() && height1 > nGrandfather && IsResearchAgeEnabled(height1) && BlockNeedsChecked(nTime) && !fLoadingIndex)

This will help in removing obsolete checks and will make it easier to move the code later on.

[jamescowens]

Done by #1572.