Optimize loading items, improve startup time

[Lancej]

These changes improve PoB startup time by about 970 ms.

main:Init() average time
Before: 2709 ms
After: 1738 ms

Changes:

• In ParseRaw first loop that creates self.rawLines now done with one gmatch call.
• processInfluenceLine function replaced with lookup table.
• "specName, specVal" parsing done with less string match calls.
• Line flags like "{crafted}" or " (implicit)" are all parsed with just 2 gsub calls instead of the many match calls like before. These 2 gsub calls also replace the many gsub calls to remove the flags from the line.
• NormaliseQuality was called at the end of ParseRaw then again in Main:Init. Instead the call from Main is moved into ParseRaw as well. I'm not sure if NormaliseQuality should have different results if you call it twice in a row but I already changed a lot and decided to leave it alone for now and just call it twice still. Moving it saved the need for calling BuildAndParseRaw for uniques.
• getLineRangeMinMax removed and replaced with a find call.
• In sanitiseItemText removed newline and space trimming gsub calls because ParseRaw line splitting already does both. Also does a find for chars 128-255 or '<' before doing the rest of the gsub calls.
• In BuildModListForSlotNum set BasePercentile variables to 1 when creating an item with no defense attributes in the raw text. This one is a bug fix and not a speed up. I added a test for this in the new file TestItemParse_spec.lua, it's the last test in that file and it failed before but passes now.
• Other smaller changes.

Steps taken to verify a working solution:

Added TestItemParse_spec.lua with a bunch of item parsing tests. Also tried loading several builds to make sure items were the same and checked items from the uniques/rares item DB.