configure.ac: Make our configure more consistent
configure.ac: Make our configure more consistent

This commit does the following changes:
 - Disable rpath by default
 - Switch all of our options to --enable-FEATURE in the help
 - Add auto-detection of libcap availability
 - Add auto-detection of python3 availability
 - Always specify the default value in --help
 - Add a configuration overview at the end

Signed-off-by: Stéphane Graber <089afc6d81f66f1168a9849e15660feae286e024@ubuntu.com>
Signed-off-by: Serge Hallyn <3df611b026e4639bee8aef7a4beb2e39fcebb313@ubuntu.com>

sapun/lxc,cjwatson/lxc,ecarrara/lxc,Pelagicore/lxc,christiaan/lxc,hfuCN/lxc,codebauss/lxc,ojkastl/lxc_Patches,rowhit/lxc,ss1h2a3tw/lxc,DarknessBeforeDawn/lxc,jirislaby/lxc,ioops/lxc,weizhenwei/lxc,yubo/lxc,caglar10ur/lxc,major/lxc,sapun/lxc,Distrotech/lxc,jirislaby/lxc,szaszg/lxc,fwilson42/lxc,raspberrypython/lxc,lisongmin/lxc,lazy404/lxc,ksperis/lxc,QingweiPeterLan/cs188-lxc,bostjan/lxc,aeris/lxc,hallyn/lxc,JohnPeacockMessageSystems/lxc,Ponce/lxc,ecarrara/lxc,hkjolhede/lxc,LynxChaus/lxc,szaszg/lxc,Pelagicore/lxc,bmoar/lxc,rldleblanc/lxc,ojkastl/lxc_Patches,tych0/lxc,hkjolhede/lxc,Ponce/lxc,major/lxc,armcc/lxc,hfuCN/lxc,GreatFruitOmsk/lxc,caglar10ur/lxc,Ponce/lxc,federicobriata/lxc,ysbnim/lxc,codebauss/lxc,yubo/lxc,lazy404/lxc,tych0/lxc,weizhenwei/lxc,caglar10ur/lxc,hallyn/lxc,rldleblanc/lxc,ss1h2a3tw/lxc,LynxChaus/lxc,ss1h2a3tw/lxc,Distrotech/lxc,major/lxc,LynxChaus/lxc,virajs/lxc,terceiro/lxc,bostjan/lxc,akshaykarle/lxc,akshaykarle/lxc,efiop/lxc,raspberrypython/lxc,GreatFruitOmsk/lxc,QingweiPeterLan/cs188-lxc,aeris/lxc,armcc/lxc,akshaykarle/lxc,Distrotech/lxc,terceiro/lxc,ioops/lxc,christiaan/lxc,JohnPeacockMessageSystems/lxc,ysbnim/lxc,bostjan/lxc,ksperis/lxc,regit/lxc,ksperis/lxc,fwilson42/lxc,ysbnim/lxc,regit/lxc,ecarrara/lxc,lisongmin/lxc,christiaan/lxc,GreatFruitOmsk/lxc,thmo/lxc,lazy404/lxc,weizhenwei/lxc,sapun/lxc,armcc/lxc,DarknessBeforeDawn/lxc,rldleblanc/lxc,hfuCN/lxc,federicobriata/lxc,thmo/lxc,raspberrypython/lxc,yubo/lxc,rowhit/lxc,cjwatson/lxc,tych0/lxc,cjwatson/lxc,federicobriata/lxc,aeris/lxc,regit/lxc,bmoar/lxc,terceiro/lxc,szaszg/lxc,rowhit/lxc,hkjolhede/lxc,QingweiPeterLan/cs188-lxc,ioops/lxc,thmo/lxc,jirislaby/lxc,JohnPeacockMessageSystems/lxc,fwilson42/lxc,codebauss/lxc,hallyn/lxc,virajs/lxc,DarknessBeforeDawn/lxc,lisongmin/lxc,ojkastl/lxc_Patches,Pelagicore/lxc,virajs/lxc,ojkastl/lxc_Patches,efiop/lxc,efiop/lxc,bmoar/lxc