Verbose Maven configure error.

Review: https://reviews.apache.org/r/21950
Adding missing files to gitignore template.

Review: https://reviews.apache.org/r/21718
Give the command executor some cpu and memory.

Review: https://reviews.apache.org/r/22251
Wait on Containerizer::update to complete before sending status update.

Review: https://reviews.apache.org/r/22253
Fix some clang compiler issues in perf code.
Minor style fix.
Enabling ZooKeeper tests that were previously disabled.

Review: https://reviews.apache.org/r/22591
MESOS-1312: Added orphan_tasks and unregistered_frameworks in
master's state.json.

Added orphan_tasks and unregistered_frameworks in state.json to display
tasks that are currently running on the slaves, but do not belong to
any already (re-)registered frameworks.

Review: https://reviews.apache.org/r/22223
Initial import for health check
Fixed Protobuf to JSON serialization of optional fields with default values.

Previously, only optional fields which where explicitly set would be serialized regardless whether default values was present.
This patch adds those fields explicitly.

Review: https://reviews.apache.org/r/21246
Cleaned up JSON work
Snapshot of current health check program.
Add task health check with custom command support