Move CXXFLAGS definitions to config.mk and thus streamline compiler flags for all Makefiles in subdirectories

- Analytics plugins can be now loaded and unloaded dynamically
- DCDBPusher now looks into the current configuration directory if no
path is supplied when loading/reloading a plugin

dcdbpusher: New PluginManager class to bundle all plugin related operations. Integration outstanding

CollectAgent should be switched to new Rest API design as soon as possible
Minor improvements to README, Makefile and PUT /analytics/reload methods

- Fixed name of log files for collectagent
- Fixed a few compilation warnings under gcc 7
- README for dcdbpusher now correctly refers to dcdbpusher.conf files
- SensorNavigator is rebuilt after plugin reloads only if data analytics
are currently running

- The multiplier used when computing percentages in the SAR ProcFS
parser has been raised to 100000 to reduce accuracy loss

- Fixed a couple minor bugs arising when only one column is selected
in the stat file
- Fixed a bug in the SAR parser

- Added the htVal parameter to the copy constructor

- a "filter" configuration parameter has been added, which is used
to discard sensor names when building the sensor navigator
- Can be used to e.g. build a sensor navigator in a collectagent
using only the sensors that are directly collected by it
- Implemented a switch to select leftmost/rightmost binary search
in CacheEntry, used for the QueryEngine

Change perf-plugin implementation: Instead of duplicating sensorGroups per CPU only one group is used with duplicated sensors

- Fixed a few warnings introduced in the latest ProcFS commit

- Virtual threads can now be automatically aggregated for procstat and
sar groups
- the htVal parameter is the number of physical threads; corresponding
virtual threads are determined via modulo arithmetic
- Minor changes to AnalyticsController in collectagent