Add IORate and first code for file configuration

NEWS

+Version 1.6
+===========
+
+    * Configuration file: user can defines limits
+    * Display limits in the help screen
+    * Add per process IO (read and write) rate in B per second
+      IO rate only available on Linux from a root account
+    * If CPU iowait alert then sort by processes by IO rate 
+    * Process column style auto (underline) or manual (bold) 
+    * Display a sort indicator (is space is available)
+    * Change the table key in the help screen 
+
 Version 1.5.2
 =============
 

glances/conf/glances.conf

+[global]
+# Defaults limits for all the stats in %
+# Defaults values if not defined: 50/70/90 
+careful=50
+warning=70
+critical=90
+
+[cpu]
+# Limits values for CPU user in %
+# Defaults values if not defined: 50/70/90 
+user_careful=50
+user_warning=70
+user_critical=90
+# Limits values for CPU system in %
+# Defaults values if not defined: 50/70/90 
+system_careful=50
+system_warning=70
+system_critical=90
+# Limits values for CPU iowait in %
+# Defaults values if not defined: 40/60/80 
+iowait_careful=40
+iowait_warning=60
+iowait_critical=80
+
+[load]
+# Value * Core
+# Defaults values if not defined: 0.7/1.0/5.0 per Core 
+careful=0.7
+warning=1.0
+critical=5.0
+
+[memory]
+# Defaults limits for free RAM memory in %
+# Defaults values if not defined: 50/70/90 
+careful=50
+warning=70
+critical=90
+
+[swap]
+# Defaults limits for free swap memory in %
+# Defaults values if not defined: 50/70/90 
+careful=50
+warning=70
+critical=90
+
+[temperature]
+# Temperatures in °C for sensors
+# Defaults values if not defined: 60/70/80 
+careful=60
+warning=70
+critical=80
+
+[filesystem]
+# Defaults limits for free filesytem space in %
+# Defaults values if not defined: 50/70/90 
+careful=50
+warning=70
+critical=90