added worker_group;
fork: default to subgroup of worker_group;
removed obsolete fork_local;
join/get_result: cumulative flattened exceptions;
map: subgroup of worker_group;
theory Isar
imports Base
begin
chapter {* Isar language elements *}
text {*
The primary Isar language consists of three main categories of
language elements:
\begin{enumerate}
\item Proof commands
\item Proof methods
\item Attributes
\end{enumerate}
*}
section {* Proof commands *}
text FIXME
section {* Proof methods *}
text FIXME
section {* Attributes *}
text FIXME
end