javadoc -> scaladoc translation

with the following replacements:

\{@link (\w+)#(\w+)\s+(\w+)\}
[[$1.$2 $3]]

\{@link (\w+)#(\w+)\((.*)\)\}
[[$1.$2($3)]]

\{@link #(\w+)\}
[[Observable.$1]]

\{@link (\w+)#(\w+)\}
[[$1.$2]]

<code>
`

</code>
`

\*\s*<p>\s*\n
*\n

\{@link (\w+)\}
[[$1]]

\{@link ((\w|\.)+)\}
[[$1]]

\[\[rx\.
[[rx.lang.scala.

\{@code\s*(([^}])+)\}
`$1`

@param <(\w+)>
@tparam $1

&lt;(\w+)&gt;
[$1]

<(\w+)>
[$1]

"timespan" argument
`timespan` argument

"timeshift" argument
`timeshift` argument

\[\[Action0\]\]
function

plus some manual replacements