Replace on_auth_fail callback with more versatile on_authplayer
Better clarify account login process in Lua API documentation
Change initial timestamp for newly registered accounts to -1
* Modernize lua read (part 2 & 3): C++ templating assurance
Implement the boolean reader
Implement the string reader
Also remove unused & unimplemented script_error_handler
Add a reader with default value
This reverts commit 362ef5f6ced862daa4733034810d0b07e2ad5d89.
Stack tracebacks couldn't be generated in LuaError::LuaError anyway and this
caused a second, empty traceback in most cases. In cases where there wasn't
annother traceback the stack had already unwound and the traceback was empty.