transactionview: add a "total amount" widget

This is useful to get the total amount of the subset of transactions
currently selected in the table below (eg, total of all stakes in
the last week, etc).
Merge pull request #2 from moneromooo/total-amount

transactionview: add a "total amount" widget
include inttypes.h
add new hard checkpoint
add block explorer as DNS seed
fix typos
comment out partial features
bitcoingui: fix network weight, etc, not updating when many peers are lagging

If the median of the peers' block count is less than our block count,
things like network weight, etc, will not be updated. If we are connected
with slow to update peers, this can mean those update very seldom.
We now update those values when we're equal or above the median value.
refine stake time estimate
Merge pull request #3 from moneromooo/peer-count

bitcoingui: fix network weight, etc, not updating when many peers are la...
update linux.pro
fix highlighting of S4C tab
fix typos
Changes for OSX Compile
Merge pull request #4 from billotronic/master

Changes for OSX Compile
S4C cleanup