Add HPX inspect tool

[hkaiser]

This patch proposes to add a fork of the Boost inspect tool to HPX. It also enables running this tool on all of the HPX' source code tree during each CircleCI build. This will ensure that a CircleCI build will fail if one or more of the rules are violated which are currently checked by the tool.

The following things have been modified from the Boost version of the inspect tool:

• Overhauled the command line handling, as a consequence the HPX inspect command line options differ from the original tool (see below for the new options)
• Added the ability to write the report to a file (--output=<file> option)
• Changed the tool's tags from boost-no-inspect to hpx-no-inspect

This patch also fixes (or suppresses) all reported violations in the HPX source code base.

Here is the output of invoking inpect --help:

Usage: inspect [dir [dir ...]] [options]:               
  -h [ --help ]                 print some command line help
  -o [ --output ] arg           the filename to write the output to 
  -t [ --text ]                 write a text file (default: html)   
  -b [ --brief ]                write a short report only (default:     
                                comprehensive)           
  --license [=arg(=0)]          check for license violations (default: off)   
  --copyright [=arg(=0)]        check for copyright violations (default: off) 
  --crlf [=arg(=0)]             check for crlf (line endings) violations   
                                (default: off)  
  --end [=arg(=0)]              check for missing newline at end of file   
                                violations (default: off)     
  --link [=arg(=0)]             check for unlinked files violations (default:   
                                off)         
  --path_name [=arg(=0)]        check for path name violations (default: off)   
  --tab [=arg(=0)]              check for tab violations (default: off)     
  --ascii [=arg(=0)]            check for non-ascii character usage violations 
                                (default: off)     
  --apple_macro [=arg(=0)]      check for apple macro violations (default: off)   
  --assert_macro [=arg(=0)]     check for plain assert usage violations    
                                (default: off)     
  --deprecated_macro [=arg(=0)] check for deprecated macro usage violations  
                                (default: off)      
  --minmax [=arg(=0)]           check for minmax usage violations (default:    
                                off)          
  --unnamed [=arg(=0)]          check for unnamed namespace usage violations 
                                (default: off)       
  -a [ --all ]                  check for all violations (default: no checks   
                                are performed)    

[hkaiser]

This pull request is open for a week now. Please review. This patch proposes a tool which is important for improving our formal code quality.

[K-ballo]

LGTM