Regex rules: rewrite rules using negative lookahead

[Shaked]

Golang uses re2 regular expression library while the rules are written for PCRE.

At the moment there are 3 rules that are effected by this issue:

`NexusTablet`:   `^.*Android.*Nexus(((?:(?!Mobile))|(?:(\s(7|10).+))).)*$`,
`AsusTablet`:     `^.*PadFone((?!Mobile).)*$|Transformer|TF101|TF101G|TF300T|TF300TG|TF300TL|TF700T|TF700KL|TF701T|TF810C|ME171|ME301T|ME302C|ME371MG|ME370T|ME372MG|ME172V|ME173X|ME400C|Slider SL101|\bK00F\b|TX201LA`,
`GenericTablet`: `Android.*\b97D\b|Tablet(?!.*PC)|ViewPad7|BNTV250A|MID-WCDMA|LogicPD Zoom2|\bA7EB\b|CatNova8|A1_07|CT704|CT1002|\bM721\b|rk30sdk|\bEVOTAB\b|SmartTabII10|SmartTab10|M758A|ET904|ALUMIUM10`,