Remove uncessary exception throwing and property map checking.

UTF8 is not strictly valid for GML, but it doesn't hurt.

With this, edge properties with convertible types are always copied,
regardless if the edge set is the same between target and source
graphs. In case the edge set is not the same, the properties are copied
only for the edges in the intersection.

This fixes issue #668

Use lambdas and pack expansion to reduce template instantiations in action_dispatch

This change produces significant reductions in compiler memory use (4.15GB to 2.81GB in my `graph_assortativity` testcase) and compiler runtime (180m to 168m overall, 206s to 188s in the testcase) by:

1. Performing type iteration with parameter pack expansion where possible
2. Testing the stored `boost::any` types sequentially instead of all at once (M+N instead of M*N operations)

I see no significant change in runtime with this approach, though it should in theory be an improvement.

See merge request count0/graph-tool!33

Improve build times through header removal and relocation

See merge request count0/graph-tool!31

- Eliminate unused headers
- reduce dependencies among headers (slightly)

The include-what-you-use tool (IWYU) was used to analyze header
dependencies and recommend fixes; some additional manual work was
then performed.

Add missing include

Ensure supplied position map for planar_layout is owned by view

See merge request count0/graph-tool!32

Mass bind -> lambda conversion

See merge request !30

Source file work done with custom-modified versions of clang-format
and clang-tidy, via the modernize-avoid-bind checker. Headers were
modified by hand. A script removed uses of <functional> and <boost/bind.hpp>.

This implements buffered io, instead of loading the entire edge list to memory.