wallet api: allow wallet to fetch all key images via api

src/wallet/api/wallet.cpp

@@ -1168,7 +1168,7 @@ bool WalletImpl::submitTransaction(const string &fileName) {
   return true;
 }
 
-bool WalletImpl::exportKeyImages(const string &filename) 
+bool WalletImpl::exportKeyImages(const string &filename, bool all) 
 {
   if (m_wallet->watch_only())
   {
@@ -1178,7 +1178,7 @@ bool WalletImpl::exportKeyImages(const string &filename)
   
   try
   {
-    if (!m_wallet->export_key_images(filename))
+    if (!m_wallet->export_key_images(filename), all)
     {
       setStatusError(tr("failed to save file ") + filename);
       return false;

src/wallet/api/wallet.h

@@ -164,7 +164,7 @@ public:
     virtual PendingTransaction * createSweepUnmixableTransaction() override;
     bool submitTransaction(const std::string &fileName) override;
     virtual UnsignedTransaction * loadUnsignedTx(const std::string &unsigned_filename) override;
-    bool exportKeyImages(const std::string &filename) override;
+    bool exportKeyImages(const std::string &filename, bool all = false) override;
     bool importKeyImages(const std::string &filename) override;
 
     virtual void disposeTransaction(PendingTransaction * t) override;

src/wallet/api/wallet2_api.h

@@ -901,9 +901,10 @@ struct Wallet
    /*!
     * \brief exportKeyImages - exports key images to file
     * \param filename
+    * \param all - export all key images or only those that have not yet been exported
     * \return                  - true on success
     */
-    virtual bool exportKeyImages(const std::string &filename) = 0;
+    virtual bool exportKeyImages(const std::string &filename, bool all = false) = 0;
    
    /*!
     * \brief importKeyImages - imports key images from file