Bump version to 2.0 and drop support for Thunderbird 17
Update jsdeferred
Show more information for debugging
Add JXON version of the configuration XML file.

JXON: https://developer.mozilla.org/ja/docs/JXON
Read configurations from JXON insteaad of E4X
Remove E4X namespace definition
Convert nsIArray to Array correctly
Fix typo: missing "e"

 mailProvider =>
emailProvider
Remove needless "achook:" prefix from configuration key
Ignore empty elements in the configuration file
Fix wrongly inverted operator

&& =>
||
Use verbose level = default JXON for the default callback
Read JXON node value correctly for verbose level = 2
Fill values to %...% placeholders
Report internal errors
Add sample configuration for GMail
Fix invalid socket type fo outgoing server
Support nsIArray or nsISimpleEnumerator type accountManager.accounts
Fix typo
Work with JXON correctly