SERVER-13635 Make BtreeInterface not Btree-specific

Implementations should be able to use any data structure that maintains
sorted order.
SERVER-14059 Allow overriding of dist architecture name in scons
SERVER-14302 SERVER-14304 Fix IDHackRunner's use of sharding filter
SERVER-13645 eliminate is_master.h
SERVER-14274 SERVER-14135 implement awaitReplication() in LegacyReplicationCoordinator
SERVER-14275 SERVER-14135 implement setLastOptime() in LegacyReplicationCoordinator
SERVER-14312 fix a failure mode of reconfig.js
SERVER-14308 eliminate majority.js
SERVER-14135 implement processReplSetGetStatus() in LegacyReplicationCoordinator
SERVER-13635 IndexAccessMethods now take a BtreeInterface rather than a RecordStore
Revert "SERVER-13635 IndexAccessMethods now take a BtreeInterface rather than a RecordStore"

This reverts commit 98a0c6f7c2a91d28a1f48c8fb0805e6745f0e8f9.
SERVER-13635 IndexAccessMethods now take a BtreeInterface rather than a RecordStore
SERVER-1153: head record store update now works
SERVER-13635: fix BtreeInterface change by removing dead variable
SERVER-13635: clean up ownership semantics of objects inside of StorageEngine
SERVER-14312 ensure node 0 will be primary as part of the reconfig.js fix