Support quotes for string values and escaping of quotes

[orchestr7]

Now we ignore quotes in parsing

[orchestr7]

Any Unicode character may be used except those that must be escaped: quotation mark, backslash, and the control characters other than tab (U+0000 to U+0008, U+000A to U+001F, U+007F).

str = "I'm a string. \"You can quote me\". Name\tJos\u00E9\nLocation\tSF."
For convenience, some popular characters have a compact escape sequence.

\b - backspace (U+0008)
\t - tab (U+0009)
\n - linefeed (U+000A)
\f - form feed (U+000C)
\r - carriage return (U+000D)
" - quote (U+0022)
\ - backslash (U+005C)
\uXXXX - unicode (U+XXXX)
\UXXXXXXXX - unicode (U+XXXXXXXX)
Any Unicode character may be escaped with the \uXXXX or \UXXXXXXXX forms. The escape codes must be valid Unicode scalar values.

All other escape sequences not listed above are reserved; if they are used, TOML should produce an error.

Sometimes you need to express passages of text (e.g. translation files) or would like to break up a very long string into multiple lines. TOML makes this easy.