Added convenience string to date and date to string functionality in QL Date class.
Merge remote-tracking branch 'lballabio/master'
Merge remote-tracking branch 'upstream/master'
Merge remote-tracking branch 'lballabio/master'
Merge branch 'master' of https://github.com/mdriesch/quantlib
merge from trunk
Merge remote-tracking branch 'upstream/master' into quantlib-merge

Conflicts:
	QuantLib/ql/experimental/processes/gemanroncoroniprocess.cpp
avoid clang++ warning
avoid clang++ warning
Backport fix from master: fixed index access
Merge pull request #34.
Moved parsing of dates to existing utility class.

Previous parsing functionality was deprecated. A few tests were added.
Renamed holder generator to "formatted_date".

It seems more descriptive and less ambiguous than "userdefined_date"
(it's the format which is user-defined, not the date).

Also, the preprocessor checks for Boost > 1.33 were removed (since
we already assume that Boost is at least at version 1.34.1).
Merge pull request #29.
fix ManipulateDistribution::convolve() QL_REQUIRE
fix CommodityCurve::dates_ and CommodityCurve::data_ leak 

each time you call CommodityCurve::setPrices()
fix potential EnergyCommodity::secondaryCostAmounts_ leak

each time you call EnergyCommodity::calculateSecondaryCostAmounts()
fix SmileSectionUtils::SmileSectionUtils() insertion values to "k_"

```C++
k_.push_back( tmp[i] * f_ );
```
was without check
fix "RecursiveCdoEngine::loss_unit_" init

before getting "std::min_element(lgds.begin(), lgds.end())"
in "lgds" removed all "0" elements. But this is not correct removing.
std::remove() only moving all the elements that not equal to "0" and return iterator to the new end.
instead of "0" lgds contains trash. There are two ways:
1. get iterator to the new end: std::min_element(lgds.begin(), new_end_iterator)
2. really erase all "0" from lgds: lgds.erase(std::remove(lgds.begin(), lgds.end(), 0.), lgds.end());

cplusplus.com/reference/algorithm/remove/

I suggest 2
add endpoints for sections with limited strike range,
move deleteArbitragePoints from KahaleSmileSection to SmileSectionUtils,
delete unused member variables,
use otm option to imply volatility from price,
reformat source code